With pneumatic tires, a side-reinforced pneumatic run flat tire in which a reinforcing rubber layer having a falcated cross-section is inserted on an inner face of a side wall portion, and by which run-flat traveling is made possible based on the rigidity of this reinforcing rubber layer is known (e.g. see Japanese Unexamined Patent Application Publication No. 2010-023823A). With such a side reinforced pneumatic run flat tire, there is a benefit in that run-flat traveling is achieved based on the tire structure without depending on a support body such as an inner ring or the like attached to the wheel, but there is also a problem in that the rigidity of the side wall portion is higher than that of a regular tire and, therefore, riding comfort when regular traveling is negatively affected.
Therefore, what are referred to as “soft run-flat tires” have been used in which the same degree of riding comfort as in a tire that does not have a reinforcing rubber layer is maintained while at least the minimum necessary run-flat durability is ensured by miniaturizing the reinforcing rubber layer as much as possible without inhibiting run-flat durability or reducing the rigidity. In particular, in recent years, it has become possible to reduce the tire rigidity without significantly inhibiting the run-flat durability. However, these run-flat tires with reduced tire rigidity tend to be easily damaged due to rupture of the carcass in an upper portion of a bead core. Therefore, run-flat durability and riding comfort when regular traveling are not necessarily both achieved, and there was still scope for improvement of both run-flat durability and riding comfort when regular traveling.